Kinetics of cluster formation in the laser vaporization source: Carbon clusters.

A general model of cluster formation in the laser vaporization source starting from the atomic vapor is developed and applied to carbon clusters. Two limiting cases of cluster growth exist: the diffusion-limited regime, in which the cluster distribution is essentially featureless, and the reaction-limited regime, in which the most stable clusters show as magic numbers in the cluster distribution. An approximation theory of the agregation kernel allows for calculation of the cluster distribution in the reaction-limited regime from the formation energies of the reacting clusters. Heat released in cluster fusion allows clusters smaller than approximately 20-40 atoms to attain their lowest or almost lowest energy configurations in both the diffusion- and reaction-limited regimes.